Movable barriers of various kinds are known in the art including pivoting or sliding doors or gates, garage doors (comprising both segmented and one-piece panels), arm guards, rolling shutters, and vertically moving fire doors, to name a few. While such barriers share a variety of design constraints, goals, and requirements, fire doors present a particularly challenging design paradigm.
Fire doors are generally intended to obstruct significant building passageways (such as hallways or stairwell entrances) through which oxygen might otherwise flow to feed an existing undesired fire. Automatic operation, at least when closing, tends to be a desired and/or required design criteria. Though automatic closure capability comprises a long-standing and even a relatively intuitive need, past solutions often leave much to be desired.
Early solutions tended to emphasize mechanical solutions. For example, a vertically movable fire door would be suspended through use of a heat-sensitive fusable link. In theory the heat of a fire would melt the fusable link and permit the fire door to close and aid in denying oxygen to the fire. In practice such a response might still permit a fire to build and destroy a considerable amount of property and/or threaten individuals in the area, so long as the fire remained distal to the fusable link. Perhaps worse, such an approach makes testing or other maintenance requirements difficult, a circumstance that runs contrary to current knowledge regarding the likelihood that a given fire door of this type will often fail when needed if the fire door and its supporting linkages, tracks, and the like are not occasionally moved, exercised, and tested.
At least partially in response to dissatisfaction with such conditions, system designers began to integrate the operation of such fire doors with other building alarm systems. So configured, a fire door would be allowed to drop into a closed position in response to an electric actuation signal from, for example, a remote fire monitor system. At the same time, at least in part to permit ease of testing such systems, designers began incorporating motors that serve to lift a fire door back into a ready position after use.
Unfortunately, such alterations have not suitably addressed all concerns regarding the controlled and/or informed movement of such barriers. For example, for the most part, such barriers tend to be relatively heavy and are allowed to fall rapidly into place by the force of gravity. This rapid and often-unannounced movement has the potential to injure people in the path of the barrier's movement and/or can trap people without effective notice or opportunity to take any proactive measures to escape from the fire. One prior art suggestion suggests that pneumatic techniques be used to slow the descent of such a fire door. While this suggestion can aid in avoiding the problems just noted, it, too tends to again give rise to undesirable circumstances. As one simple example, there are times when a rapid descent is utterly appropriate and desired. Such a pneumatically controlled descent can be so slow as to permit a given fire to gain the advantage and defeat the intended result of the barrier closure.
There are other problems and concerns that are particularly keen when associated with fire doors. Centrally-architected alarm systems may or may not be able to effectively transmit useful control signals to various fire doors as located throughout a given building, with a likelihood of control failure being at least partly correlated to the size and behavior of a given fire, to some extent, the more devastating the conflagration the more likely a centrally-based control system will fail to effect closure of at least some fire doors.
Yet another problem can arise once a fire door has closed. That is, such a door can impede needed access by fire fighters. In general, however, it can be counterproductive to provide a simple and readily available mechanism to effect the opening of such a barrier because opening the barrier can, under some circumstances, be highly dangerous. Manipulation of such a control by unauthorized individuals or by fire fighters who are ignorant of conditions on the other side of the door can present considerable risk to local individuals and can also contribute to an unintended spreading of the fire.